Filler-containing polypropylene resin composition and process for producing the same

ABSTRACT

A filler-containing polypropylene resin composition and a process for producing the same are disclosed. The composition comprises (a) from 27 to 87% by weight of a polypropylene resin, (b) from 3 to 15% by weight of a modified polypropylene resin containing from 0.1 to 3 mol % of an unsaturated dicarboxylic acid anhydride repeating unit, (c) from 5 to 30% by weight of an ethylene copolymer composed of from 82 to 98.7 mol % of an ethylene repeating unit, from 1 to 15 mol % of an ester repeating unit selected from alkyl acrylates and alkyl methacrylates having from 1 to 8 carbon atoms in the alkyl moiety thereof, and from 0.3 to 3 mol % of an unsaturated dicarboxylic acid anhydride repeating unit, and (d) from 5 to 40% by weight of a filler. The process comprises melt-mixing the components (a), (b) and (d) and then melt-mixing the resulting mixture with the component (c). The resin composition exhibits excellent finishing properties, such as adhesion, coating properties, and printability, as well as improved rigidity and thermal properties.

FIELD OF THE INVENTION

This invention relates to a filler-containing polypropylene resincomposition and a process for producing the same. More particularly, itrelates to a filler-containing polypropylene resin composition havingimproved finishing properties and a process for producing the same.

BACKGROUND OF THE INVENTION

In recent years, applications of filler-containing polypropylene resinsto automobile parts and appliances have been markedly broadened becauseof their excellent mechanical and thermal properties.

In the application to automobile parts, for instance, interior parts,such as an instrument board, a trim, and a pillar-post, are oftencovered with non-woven fabric, foamed fabric, leather cloth made ofpolyvinyl chloride, and the like to produce an atmosphere of high-class.Further, there is noted a tendency to coat a bumper in color harmonywith the body in a decorative style. In appliance parts, also, printingis commonly employed for decoration.

Polypropylene resins often find difficulty in finishing due to theirpoor adhesion or coating properties arising from non-polarity. It iswell known to add fillers to polypropylene resins in order to improvethese finishing properties. Incorporation of fillers improves finishingproperties to some extent depending on the kind and amount of thefiller, but such an improvement is still insufficient for practical use.

In order to further improve finishing properties, i.e., compatibilitybetween polypropylene and adhesives or coatings, a medium called"primer", which typically comprises chlorinated polypropylene andtoluene, etc., is usually provided therebetween. However, since theprimer itself is expensive and an extra coating step is required, thecost of the final products is so increased. Therefore, furtherimprovements have been demanded.

In an attempt to improve surface properties, physical or chemicaletching of the surface of polypropylene molded products prior toadhesion has been studies and applied to practice. However, this processinvolves more complicated steps than the primer coating, and someconditions of etching cause deformation of molded products or produceinsufficient effects.

In the case of coating, the process of coating a primer is being shiftedto a process comprising oxidatively polarizing the surface of moldedarticles by irradiation with plasma to improve coating properties. Underthe present situation, however, this process does not always achievesatisfactory results because the plasma irradiation should be effectedin a batch system and the polarity obtained is non-uniform depending onthe shape of the molded articles.

Attempts have also been made to impart polarity to polypropylene per se.For example, it has been proposed to modify polypropylene by graftingwith an unsaturated carboxylic acid or an anhydride thereof, e.g.,acrylic acid, maleic anhydride, etc., in the presence of an initiator,e.g., organic peroxides, or to blend the above-described modifiedpolypropylene with unmodified polypropylene, as disclosed in JapanesePatent Application (OPI) No. 76149/75 (the term "OPI" as used hereinmeans "unexamined published application"), Japanese Patent PublicationNo. 10264/77, etc.

According to these processes, the grafting is accompanied bydecomposition of polypropylene with the peroxide so that the amount ofthe unsaturated carboxylic acid or the anhydride thereof to beincorporated is limited. As a result, the surface modifying effectattained is insufficient. If any effects are produced, mechanicalproperties are impaired due to molecular weight reduction ofpolypropylene.

In order to overcome these disadvantages associated with theconventional polypropylene resins, the present inventors proposed acomposition comprising a polypropylene resin, an ethylene copolymercomposed of an ethylene unit, an ester unit selected from alkylacrylates and alkyl methacrylates, and an unsaturated dicarboxylic acidanhydride unit, and a filler, as disclosed in European Pat. No.213,720A.

However, the aforesaid filler-containing polypropylene resin compositionis insufficient in manifestation of the effects of fillers to improverigidity and also exhibits unsatisfactory thermal properties, althoughsurface modifying effects can be achieved as expected.

SUMMARY OF THE INVENTION

One object of this invention is to provide a filler-containingpolypropylene resin composition having excellent finishing properties,such as adhesion, coating properties, printability, and the like, aswell as improved mechanical and thermal properties.

Another object of this invention is to provide a process for producingsuch a filler-containing polypropylene resin composition.

The inventors have conducted extensive investigations on improvements ofthe above-described filler-containing polypropylene resin composition ofEuropean Pat. No. 213,720A. As a result, it has now been found thatmarked improvements on rigidity and thermal properties can be obtainedby incorporating a modified polypropylene resin containing anunsaturated dicarboxylic acid anhydride repeating unit into theaforesaid composition.

The filler-containing polypropylene resin composition according to thepresent invention comprises

(a) from 27 to 87% by weight of a polypropylene resin.

(b) from 3 to 15% by weight of a modified polypropylene resin containingfrom 0.1 to 3 mol % of an unsaturated dicarboxylic acid anhydriderepeating unit,

(c) from 5 to 30% by weight of an ethylene copolymer composed of from 82to 98.7 mol % of an ethylene repeating unit, from 1 to 15 mol % of anester repeating unit selected from alkyl acrylates and alkylmethacrylates having from 1 to 8 carbon atoms in the alkyl moietythereof, and from 0.3 to 3 mol % of an unsaturated dicarboxylic acidanhydride repeating unit, and

(d) from 5 to 40% by weight of a filler.

The process for producing the above-described filler-containingpolypropylene resin composition comprising components (a) to (d)comprises melt-mixing components (a), (b), and (d) to obtain (e) amixture and then melt-mixing mixture (e) with component (c).

DETAILED DESCRIPTION OF THE INVENTION

The polypropylene resins which can be used in the present inventioninclude crystalline polypropylene, crystalline propylene-ethylene blockor random copolymers, crystalline propylene-α-olefin copolymers whereinthe α-olefin has from 4 to 10 carbon atoms, and mixtures thereof.

The polypropylene resin usually has a melt index (as determinedaccording to JIS K6758) ranging from 0.5 to 100, and preferably from 1to 50, g/10 min.

The modified polypropylene resins which can be used as component (b)comprise the above-described polypropylene resin and from 0.1 to 3 mol %of an unsaturated dicarboxylic acid anhydride repeating unit. Monomersproviding the unsaturated dicarboxylic acid anhydride repeating unitinclude maleic anhydride, citraconic anhydride, itaconic anhydride,tetrahydrophthalic anhydride, etc., with maleic anhydride beingpreferred.

If the content of the unsaturated dicarboxylic acid anhydride repeatingunit in the component (b) is less than 0.1 mol %, effects of improvingcoating properties, printability, adhesion, and the like are notproduced. If it exceeds 3 mol %, the amount of polar groups introducedbecomes excessive to deteriorate compatibility with the polypropyleneresin.

The modified polypropylene resin can be obtained by known techniques,such as a process in which a polypropylene resin is dissolved in anorganic solvent and adding an unsaturated dicarboxylic acid anhydrideand a radical generator thereto, followed by heating with stirring, anda process in which all the components are fed to an extruder to effectgraft copolymerization.

Monomers providing the ethylene repeating unit in the ethylene copolymerof the present invention include methyl acrylate, ethyl acrylate, butylacrylate, methyl methacrylate, ethyl methacrylate, 2-ethylhexylmethacrylate, butyl methacrylate, etc. (hereinafter referred to asunsaturated ester compounds).

The ester repeating unit is present in the ethylene copolymer in aproportion of from 1 to 15 mol %, and preferably from 3 to 12 mol %.Proportions out of this range deteriorate compatibility of the ethylenecopolymer with the polypropylene resin or reduce the effects ofimproving mechanical characteristics, such as impact strength.

Monomers providing the unsaturated dicarboxylic acid anhydride repeatingunit include maleic anhydride, citraconic anhydride, itaconic anhydride,tetrahydrophthalic anhydride, and the like, with maleic anhydride beingparticularly preferred.

The proportion of the unsaturated dicarboxylic acid anhydride repeatingunit in the ethylene copolymer ranges from 0.3 to 3 mol %, andpreferably from 0.5 to 2.8 mol %. With proportions lower than 0.3 mol %,the amount of polar groups which contribute to finishing is too small toproduce satisfactory improving effects. Proportions higher than 3 mol %deteriorate compatibility with polypropylene resins due to excessivelystrong polarity.

Processes for producing the ethylene copolymer are not particularlyrestricted and include known processes, such as solution polymerization,emulsion polymerization, high-pressure bulk polymerization, and thelike. Of these processes, the high-pressure polymerization technique isthe most common, in which ethylene is copolymerized in the presence of aradical generator at a temperature of from 100° to 300° C. under apressure of from 500 to 3000 atm. in the presence or absence of anappropriate solvent or a chain transfer agent. The high-pressurepolymerization is suitably carried out by dissolving the above-describedunsaturated dicarboxylic acid anhydride in the above-describedunsaturated ester compound, elevating the solution in pressure by meansof a pressure pump, and introducing the solution directly into a vesseltype reactor or a tubular reactor. The thus obtained ethylene copolymerhas a melt index (as determined according to JIS K6760) of from 0.5 to800, and preferably from 1 to 200, g/10 min.

If the melt index of the ethylene copolymer is smaller than theabove-recited lower limit, the ethylene copolymer lacks compatibilitywith the polypropylene resins. Melt indices higher than the upper limitgreatly reduce rigidity, heat resistance or surface hardness of theresulting resin composition.

Fillers to be used in the present invention, either organic orinorganic, are not particularly restricted, and preferably includeinorganic fillers, such as calcium carbonate, talc, clay, silica,diatomaceous earth, alumina, zinc white, magnesium oxide, mica, calciumsulfite, calcium sulfate, calcium silicate, glass powders, glass fibers(inclusive of silane-treated glass fibers), asbestos, gypsum fibers, andthe like; and organic fillers, such as various kinds of woodmeals,cellulose fibers, melamine powders, and the like. These fillers may beused either individually or, if desired, in combination thereof. In viewof a favorable balance of impact resistance and heat resistance of theresulting filler-containing polypropylene resin composition, talc and/ormica are preferably used as fillers.

If desired, the filler to be used in the present invention can besubjected to surface treatment to ensure a good balance between rigidityand impact strength. Examples of the surface treating agent to be usedare organosilane compounds including vinyltriethoxysilane,vinyltris(β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane,γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane,N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane,N-(β-aminoethyl)-γ-aminopropylmethyltrimethoxysilane,γ-glycidoxymethoxysilane, etc. Of these,N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane andN-(β-aminoethyl)-γ-aminopropylmethyltrimethoxysilane are preferredbecause of their high reactivity to produce a filler-containingpolypropylene resin composition of highest level in balance betweenrigidity and impact strength.

The surface treating agent is usually used in an amount of from 0.1 to1.5 part by weight, and preferably from 0.3 to 1.0 part by weight, per100 parts by weight of a filler. If the amount of the surface treatingagent is less than 0.1 part by weight, the bonding strength between thecomponent (a) and the components (b) and (d) is insufficient so that theeffect of the filler to improve rigidity cannot be produced and theimpact strength becomes inferior. If it exceeds the upper limit, theeffect of the surface treating agent uneconomically comes to saturation.The surface treatment is preferably performed by the use of a ribbonmixer, a supermixer, etc.

The proportion of the component (a) in the composition of the presentinvention ranges from 27 to 87% by weight. If it is less than 27% byweight, heat resistance and rigidity as expected cannot be obtained. Ifit exceeds 87% by weight, the proportions of the components (b) and (c)are so small that adhesion and coating properties of the resultingcomposition are deteriorated and also the proportion of the component(d) is too small to exhibit rigidity.

The proportion of the component (b) in the composition ranges from 3 to15% by weight, and preferably from 5 to 15% by weight. If it is lessthan 3% by weight, the effects of improving coating properties,printability, and adhesion are insubstantial. If it exceeds 15% byweight, physical properties, such as impact strength, are reduced.

The proportion of the component (c) in the composition ranges from 5 to30% by weight, and preferably from 10 to 20% by weight. When it is lessthan 5% by weight, no substantial effects of improving adhesion, coatingproperties, and printability are produced. If it exceeds 30% by weight,the resulting composition has reduced physical properties, such asrigidity and heat resistance, and enjoys no further effects on finishingproperties.

The proportions of the component (d) in the composition is from 5 to 40%by weight, and preferably from 10 to 40% by weight. If it is less than5% by weight, improved rigidity that is an essential requirement of thecomposition according to the present invention cannot be ensured. On theother hand, proportions exceeding 40% by weight seriously reduce impactresistance of the composition, resulting in poor utility as materialsfor interior and exterior automobile parts. No further effects inimproving thermal characteristics are produced by such an excessivefiller.

In the preparation of the filler-containing polypropylene composition inaccordance with the present invention, the components (a) to (d) may bemelt-kneaded all at once, but in a preferred embodiment, the kneading iscarried out in two divided steps. That is, the components (a), (b), and(d) are melt-mixed to prepare (e) a mixture in the first step. Themixture (e) is then melt-kneaded with the component (c) to obtain theresin composition of the present invention. By this embodiment, a goodbalance of physical properties of molded products can be furtherensured.

If desired, the filler-containing polypropylene resin composition of thepresent invention can further contain various styrene-based elastomers,such as a styrene-butadiene random copolymer, a styrene-butadiene blockcopolymer, and hydrogenated products thereof; various polyolefinelastomers, such as a non-crystalline ethylene-propylene copolymer andan ethylene-propylenedicyclopentadiene copolymer; and, in addition,various functional group-containing polyolefins, such as a glycidylgroup-containing ethylene copolymer; as long as various characteristicspossessed by the resin composition of the invention are notsubstantially impaired.

The resin composition of the present invention can furthermore containappropriate amounts of various additives, such as antioxidants,weathering agents, antistatics, foaming agents, colorants, and the like.

For mixing the components, apparatus commonly employed for plastics orrubbers, such as a Banbury mixer, a single-screw extruder, a twin-screwextruder, and a roll mill, can be used. Considering that the resincomposition in a molten state shows adhesion to metal surfaces due toits polarity, mixing is desirably carried out by means of an extruder.In particular, an extruder having two or more feed zones is economicallybenificial because the first and second melt-kneading can be effectedthrough one operation.

The resin composition obtained by the present invention can be moldedinto desired molded products by injection molding, extrusion molding,blow molding, etc., in a known manner.

The filler-containing polypropylene resin composition in accordance withthe present invention possesses excellent finishing properties, such asadhesion, coating properties and printability, as well as excellentmechanical properties. In addition, the following advantages can bedrawn from the resin composition of the present invention.

(1) The resin composition can produce injection molded products having acomplicated shape and a small thickness under conventional moldingconditions while substantially retaining flowability inherent tofiller-containing polypropylene resins.

(2) The resin composition does not suffer from great reduction inmechanical characteristics, such as rigidity. In particular, thecomposition has markedly improved impact strength.

(3) Weldlines (a defect of molded products caused by incomplete fusionof two or more flows of molten resins) are not so conspicuous as in thecase of using the conventional filler-containing polypropylene resins.

Since the filler-containing polypropylene resin compositions accordingto the present invention bring about excellent effects as set forthabove, they can be utilized in the fields requiring finishing, such asadhesion, coating, and printing. Typical examples of their use includeexterior parts of automobiles, e.g., a bumper, a bumper corner, etc.,interior parts of automobiles, e.g., an instrument board, a meter case,a glove compartment, a console box, a trim, a pillar-post, etc.,motorcycle parts, e.g., a fender, a leg seal, etc., and appliance parts,e.g., a lid of a washing machine, a body of a vacuum cleaner, a stand ofan electric fan, a frame of a ventilating fan, etc.

This invention will now be illustrated in greater detail by way of thefollowing examples, but it should be understood that they are notintended to limit the present invention. All the parts and percents inthese examples are given by weight unless otherwise indicated.

In these examples, an ethylene copolymer as component (c) was preparedas follows:

Ethylene containing a small amount of propane as a chain transfer agentand maleic anhydride were dissolved in an unsaturated ester compound,and the solution was continuously fed under pressure to a 1.2 l-volumereaction vessel equipped with a stirrer. Copolymerization was effectedat a temperature controlled to 180° C. under a pressure of 1600 kg/cm²at a rate of 1.5 to 3.2 kg/hr to obtain an ethylene copolymer.

Evaluations of physical properties of the resin compositions were madein accordance with the following test methods:

(1) Wet Tensile Strength:

Measured in accordance with JIS K6768-1977 at 23° C. Specimens undertest were prepared by molding the resin composition into a plate of 150mm×90 mm×2 mm by the use of an in-line screw type injection moldingmachine of 3.5 oz. (manufactured by Nissei Jushi Kogyo K.K.).

(2) Adhesive Strength:

The same specimen as used in (1) above was coated with about 150 g/m² ofan adhesive comprising 97% by weight of G 250 (produced by Cemedine Co.,Ltd.) and 3% by weight of Desmodur (produced by Bayer AG) with anair-spray gun, followed by heating at 80° C. for 2 minutes.

A skin material (PPX, produced by Toray Industries, Inc.) was heated at110° C. for 2 minutes and, immediately thereafter, adhered to theadhesive-coated test plate under a planer pressure of 0.2 kg/cm². Afterthe laminate was allowed to stand at 23° C. and 65±5% RH for 7 days,peel test was conducted to measure a peel strength.

(3) Initial Adhesion:

The same specimen as used in (1) above was cleaned with1,1,1-trichloroethane vapors (74° C.) for 30 minutes, followed by dryingat room temperature. A urethane coat (Flexthane® #101, produced byNippon Bee Chemical Co., Ltd.) was directly spray-coated on the plateand then baked in an oven at 120° C. for 30 minutes.

The coating film was cross-hatched with a blade to make 2-millimetersquares (100 squares; 10 by 10). A 24 mm wide adhesive tape (Cellotape®,produced by Nichiban Co., Ltd.) was adhered thereon by pressing withfingers, and one end thereof was rapidly peeled off. The number of thesquares remaining on the plate was counted to determine a percentremaining.

(4) Izod Impact Strength:

Measured in accordance with JIS K7110 at 23° C. The specimens wereprepared by molding the resin composition by the use of an in-line screwtype injection molding machine of 10 oz. (manufactured by Sumitomo HeavyIndustries, Ltd.).

(5) Heat Deformation Temperature:

Measured in accordance with JIS K7202 at a bending stress of 4.6 kg/cm².The specimens were prepared in the same manner as in (4) above.

(6) Modulus in Flexure:

Measured in accordance with JIS K7203 at 23° C. The specimens wereprepared in the same manner as in (4) above.

EXAMPLES 1 TO 5 AND COMPARATIVE EXAMPLES 1 TO 5

Ethylene copolymers (a) to (d) were prepared using maleic anhydride andan unsaturated ester compound as shown in Table 1 below.

                  TABLE 1                                                         ______________________________________                                        Comonomer Content (mol %)  Melt Index                                                 Maleic    Unsaturated      (190° C.,                           Sample No.                                                                            Anhydride Ester Compound   g/10 min)                                  ______________________________________                                        (a)     1.22      butyl acrylate                                                                               5.34                                                                              150                                      (b)     1.10      2-ethylhexyl   2.81                                                                               5                                                         methacrylate                                                (c)     2.21      ethyl acrylate                                                                               7.52                                                                              41                                       (d)     1.95      methyl methacrylate                                                                         14.4 24                                       ______________________________________                                    

A polypropylene resin (Sumitomo Noblen® AW 564, a trade name for anethylene/propylene block copolymer produced by Sumitomo Chemical Co.,Ltd.; melt index: 8 g/10 min; ethylene content: 6%; ethylene content inthe propylene/ethylene copolymer unit: 40%; intrinsic viscosity of thepropylene/ethylene copolymer unit in a tetralin solution at 135° C.: 8dl/g), a modified ethylene/propylene copolymer containing 0.3 mol % ofmaleic anhydride (ethylene content: 10%; hereinafter referred to as A),each of the ethylene copolymers (a) to (d), a filler [talc having a meanparticle size (corresponding to a 50% cumulative distribution bysedimentation-type particle size distribution measurement) of 3.0 μm ormica having a mean particle size of 3.5 μm] were blended at acompounding ratio shown in Table 2, and 0.2 part of Irganox® 1010(produced by Chiba-Geigy AG), 0.05 part of calcium stearate, and 0.05part of Ultranox® 626 (produced by Borg-Warner Corp.) per 100 parts ofthe total amount of the aforesaid components were also blended in a dryblender.

The dry blend was melt-kneaded in a vented extruder having a diameter of65 mm (L/D=28, manufactured by Ikegai Iron Works, Ltd.) at a dietemperature of 220° C. to obtain a resin composition in the form ofpellets.

Each of the resulting resin compositions was evaluated for physicalproperties according to the above-described test methods, and theresults obtained are shown in Table 3.

As is apparent from the Table, the molded products obtained from thefiller-containing polypropylene resin compositions according to thepresent invention exhibit excellent performance properties, such asadhesion, coating properties, and the like, as compared with thecomparative samples.

                                      TABLE 2                                     __________________________________________________________________________           Polyproplene Resin  Ethylene Copolymer                                                                        Modified Polypropylene                                                                     Filler                    Example No.                                                                          Kind       Amount (wt %)                                                                          Kind                                                                             Amount (wt %)                                                                          Kind                                                                              Amount (wt %)                                                                          Kind                                                                             Amount (wt             __________________________________________________________________________                                                           %)                     Example 1                                                                            Sumitomo Noblen ®                                                                    45       (a)                                                                              15       A   10       talc                                                                             30                            AW 564                                                                 Example 2                                                                            Sumitomo Noblen ®                                                                    45       (b)                                                                              15       A   10       "  30                            AW 564                                                                 Example 3                                                                            Sumitomo Noblen ®                                                                    45       (c)                                                                              15       A   10       "  30                            AW 564                                                                 Example 4                                                                            Sumitomo Noblen ®                                                                    45       (d)                                                                              15       A   10       "  30                            AW 564                                                                 Example 5                                                                            Sumitomo Noblen ®                                                                    45       (c)                                                                              15       A   10       mica                                                                             30                            AW 564                                                                 Comparative                                                                          Sumitomo Noblen ®                                                                    70       --          --           talc                                                                             30                     Example 1                                                                            AW 564                                                                 Comparative                                                                          Sumitomo Noblen ®                                                                    50       (a)                                                                              15       --           "  30                     Example 2                                                                            AW 564                                                                 Comparative                                                                          Sumitomo Noblen ®                                                                    60       (b)                                                                              15       --           "  30                     Example 3                                                                            AW 564                                                                 Comparative                                                                          Sumitomo Noblen ®                                                                    60       (c)                                                                              15       --           "  30                     Example 4                                                                            AW 564                                                                 Comparative                                                                          Sumitomo Noblen ®                                                                    60       (d)                                                                              15       --           "  30                     Example 5                                                                            AW 564                                                                 __________________________________________________________________________

                  TABLE 3                                                         ______________________________________                                                 Wet                 Initial                                                   Tensile   Adhesive  Adhe- Izod Impact                                         Strength  Strength  sion  Strength                                   Example No.                                                                            (dyne/cm) (g/25 mm) (%)   (kg · cm/cm)                      ______________________________________                                        Example 1                                                                              33        4200      100   8                                          Example 2                                                                              33        4000      100   8                                          Example 3                                                                              34        4500      100   9                                          Example 4                                                                              34        4400      100   8                                          Example 5                                                                              34        4500      100   6                                          Comparative                                                                            29        1500       0    4                                          Example 1                                                                     Comparative                                                                            31        3400       70   8                                          Example 2                                                                     Comparative                                                                            31        3000       60   7                                          Example 3                                                                     Comparative                                                                            31        3500       90   8                                          Example 4                                                                     Comparative                                                                            31        3300       80   8                                          Example 5                                                                     ______________________________________                                    

EXAMPLES 6 TO 22 AND COMPARATIVE EXAMPLE 6

Sumitomo Noblen® AW564, a modified ethylene/propylene copolymer having0.3 mol % of maleic anhydride (ethylene content: 10%; hereinafterreferred to as PP-II), a modified ethylene/propylene copolymer having0.05 mol % of maleic anhydride (ethylene content: 10%; hereinafterreferred to as PP-III), each of the ethylene copolymers (a) to (d) asprepared in Example 1, a filler (talc having a mean particle size of 3.0μm and/or mica having a particle size of 3.5 μm), a surface treatingagent for the filler hereinafter described, and 0.02 part of Irganox®1010, 0.05 part of calcium stearate, and 0.05 part of Ultranox® 626 per100 parts of the total amount of the above-described components wereblended in a dry blender. The resulting blend was melt-kneaded by meansof the same extruder as used in Example 1 to obtain a filler-containingpolypropylene resin composition.

The surface treating agent for the filler used wasγ-aminopropyltriethoxysilane (TSL 8331),N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (TSL 8340),N-(β-aminoethyl)-γ-aminopropylmethyltrimethoxysilane (TSL 8345),γ-glycidoxypropyltrimethoxysilane (TSL 8350), orγ-methacryloxypropyltrimethoxysilane (TSL 8370), all produced by ToshibaSilicone K.K.

In Examples 6 and 7 and Comparative Example 6, all the above componentswere melt-kneaded at a compounding ratio shown in Table 4 through onestep.

In each of Examples 8 to 22, the components shown in the upper row ofTable 4 were first melt-kneaded at a compounding ratio indicated thereinto once obtain a pellet mixture, and the resulting mixture was thenmelt-kneaded with the components shown in the lower row of Table 4 at acompounding ratio shown therein. Taking Example 14 for instance,Sumitomo Noblen® AW 564, PP-II, and talc having been treated with TSL8340 (1% based on talc) were first melt-kneaded at a weight ratio of55/5/30 to prepare a pellet mixture. In other words, the ratio of thesethree components based on 100 parts by weight of the resulting mixturewas 61.1/5.6/33.3. The resulting pellet mixture was then melt-kneadedwith the ethylene copolymer (c) at a weight ratio of 90/10.

Each of the resulting resin compositions was evaluated for physicalproperties, and the results obtained are shown in Table 5.

It can be seen from Table 5 that a good balance of physical propertiescan be ensured by kneading the compounding components in two dividedsteps.

                                      TABLE 4                                     __________________________________________________________________________           Polypropylene Resin                                                                        Ethylene Copolymer                                                                        Modified Polypropylene                        Example No.                                                                          Kind Amount (wt %)                                                                         Kind                                                                              Amount (wt %)                                                                         Kind Amount (wt %)                            __________________________________________________________________________    Example 6                                                                            AW 564                                                                             55      (c) 10      PP-II                                                                              5                                        Example 7                                                                            "    55      (c) 10      "    5                                        Example 8                                                                            "    55      --  --      "    5                                                            (c) 10                                                    Example 9                                                                            "    55      --  --      "    5                                                            (c) 10                                                    Example 10                                                                           "    55      (c) 10      "    5                                        Example 11                                                                           "    59      --  --      "    1                                                            (c) 10                                                    Example 12                                                                           "    45      --  --      PP-III                                                                             15                                                           (c) 10                                                    Example 13                                                                           "    40      --  --      PP-II                                                                              20                                                           (c) 10                                                    Example 14                                                                           "    55      --  --      "    5                                                            (c) 10                                                    Example 15                                                                           "    55      --  --      "    5                                                            (c) 10                                                    Example 16                                                                           "    55      --  --      "    5                                                            (c) 10                                                    Example 17                                                                           "    55      --  --      "    5                                                            (c) 10                                                    Example 18                                                                           "    55      --  --      "    5                                                            (c) 10                                                    Example 19                                                                           "    50      --  --      "    10                                                           (c) 10                                                    Example 20                                                                           "    50      --  --      "    10                                                           (a) 10                                                    Example 21                                                                           "    50      --  --      "    10                                                           (b) 10                                                    Example 22                                                                           "    50      --  --      "    10                                                           (d) 10                                                    Comparative                                                                          "    70      (c)         --   --                                       Example 6                                                                     __________________________________________________________________________           Filler                  Surface Treating Agent                         Example No.                                                                          Kind                                                                              Amount (wt %)                                                                         Kind                                                                              Amount (wt %)                                                                         Kind   Amount (wt %*)                          __________________________________________________________________________    Example 6                                                                            talc                                                                              30      --  --      --    --                                       Example 7                                                                            "   30      --  --      TSL8340                                                                             1.0                                      Example 8                                                                            "   30      --  --      "      0.03                                    Example 9                                                                            "   30      --  --      "     2.5                                      Example 10                                                                           --  --      --  --      --    --                                              talc                                                                              30                  TSL8340                                                                             1.0                                      Example 11                                                                           "   30      --  --      "     1.0                                      Example 12                                                                           "   30      --  --      "     1.0                                      Example 13                                                                           "   30      --  --      "     1.0                                      Example 14                                                                           "   30      --  --      "     1.0                                      Example 15                                                                           "   30      --  --      TSL8345                                                                             1.0                                      Example 16                                                                           "   30      --  --      TSL8331                                                                             1.0                                      Example 17                                                                           "   30      --  --      TSL8350                                                                             1.0                                      Example 18                                                                           "   30      --  --      TSL8370                                                                             1.0                                      Example 19                                                                           "   25      mica                                                                              5       TSL8340                                                                             1.0                                      Example 20                                                                           "   25      "   5       "     1.0                                      Example 21                                                                           "   25      "   5       "     1.0                                      Example 22                                                                           "   25      "   5       "     1.0                                      Comparative                                                                          talc                                                                              30      --  --      --    --                                       Example 6                                                                     __________________________________________________________________________     Note: *Based on the filler or fillers.                                   

                                      TABLE 5                                     __________________________________________________________________________           Wet Tensile                                                                          Adhesive                                                                            Initial                                                                            Izod Impact                                                                           Heat Deformation                                                                       Modulus in                                 Strength                                                                             Strength                                                                            Adhesion                                                                           Strength                                                                              Temperature                                                                            Flexture                            Example No.                                                                          (dyne/cm)                                                                            (g/25 mm)                                                                           (%)  (kg · cm/cm)                                                                 (°C.)                                                                           (kg/cm.sup.2)                       __________________________________________________________________________    Example 6                                                                            32     3600  100  7       101      11500                               Example 7                                                                            32     3600  100  7       108      13300                               Example 8                                                                            32     3600  100  7       108      13500                               Example 9                                                                            32     3600  100  10      129      18500                               Example 10                                                                           32     3600  100  7       108      13300                               Example 11                                                                           32     3400  100  7       108      13100                               Example 12                                                                           32     3400  100  7       108      13500                               Example 13                                                                           33     4400  100  10      130      18800                               Example 14                                                                           32     3600  100  8       127      17200                               Example 15                                                                           32     3600  100  8       127      17000                               Example 16                                                                           32     3700  100  8       123      16100                               Example 17                                                                           32     3600  100  8       109      14200                               Example 18                                                                           32     3500  100  7       112      14800                               Example 19                                                                           33     4700  100  8       129      21100                               Example 20                                                                           33     4500  100  8       129      20500                               Example 21                                                                           33     4500  100  8       132      22000                               Example 22                                                                           34     4800  100  8       130      21500                               Comparative                                                                          29     1500   0   4       137      12800                               Example 6                                                                     __________________________________________________________________________

As described above, the filler-containing polypropylene resincompositions according to the present invention and molded productsobtained therefrom have improved finishing properties, such as adhesion,coating properties, and printability, combined with impact resistanceand heat resistance, as compared with the conventional compositions.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

What is claimed is:
 1. A filler-containing polypropylene resincomposition comprising:(a) from 27 to 87% by weight of a polypropyleneresin, (b) from 3 to 15% by weight of a modified polypropylene resincontaining from 0.1 to 3 mol % of an unsaturated dicarboxylic acidanhydride repeating unit, (c) from 5 to 30% by weight of an ethylenecopolymer composed of from 82 to 98.7 mol % of an ethylene repeatingunit, from 1 to 15 mol % of an ester repeating unit selected from alkylacrylates and alkyl methacrylates having from 1 to 8 carbon atoms in thealkyl moiety thereof, and from 0.3 to 3 mol % of an unsaturateddicarboxylic acid anhydride repeating unit, and (d) from 5 to 40% byweight of a filler.
 2. A filler-containing polypropylene resincomposition as in claim 1, wherein said unsaturated dicarboxylic acidanhydride repeating unit in the component (b) is a maleic anhydriderepeating unit.
 3. A filler-containing polypropylene resin compositionas in claim 1, wherein said unsaturated dicarboxylic acid anhydriderepeating unit in the component (c) is a maleic anhydride repeatingunit.
 4. A filler-containing polypropylene resin composition as in claim1, wherein said filler is selected form the group consisting of talc,mica and mixture thereof.
 5. A filler-containing polypropylene resin asin claim 1, wherein said filler has been treated with from 0.05 to 2% byweight of an aminosilane compound based on the filler.
 6. Afiller-containing polypropylene resin as in claim 5, wherein saidaminosilane compound is selected form the group consisting ofN-(β-aminoethyl)-γ-aminopropyltrimethoxylsilane,N-(β-aminoethyl)-γ-aminopropylmethyl-trimethyoxysilane and mixturesthereof.